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mips,kgdb: fix recursive page fault with CONFIG_KPROBES 

This fault was detected using the kgdb test suite on boot and it
crashes recursively due to the fact that CONFIG_KPROBES on mips adds
an extra die notifier in the page fault handler.  The crash signature
looks like this:

kgdbts:RUN bad memory access test
KGDB: re-enter exception: ALL breakpoints killed
Call Trace:
[<807b7548>] dump_stack+0x20/0x54
[<807b7548>] dump_stack+0x20/0x54

The fix for now is to have kgdb return immediately if the fault type
is DIE_PAGE_FAULT and allow the kprobe code to decide what is supposed
to happen.

Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This commit is contained in:
Jason Wessel 2012-08-10 12:21:15 -05:00
parent f30fed10c4
commit f0a996eeed
1 changed files with 9 additions and 0 deletions
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9
arch/mips/kernel/kgdb.c
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@ -283,6 +283,15 @@ static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd,
struct pt_regs *regs = args->regs;
int trap = (regs->cp0_cause & 0x7c) >> 2;
#ifdef CONFIG_KPROBES
/*
* Return immediately if the kprobes fault notifier has set
* DIE_PAGE_FAULT.
*/
if (cmd == DIE_PAGE_FAULT)
return NOTIFY_DONE;
#endif /* CONFIG_KPROBES */
/* Userspace events, ignore. */
if (user_mode(regs))
return NOTIFY_DONE;